Not sure why "Big 5 Big TIFF". Big 5 is either a sporting goods store, or a way of coding Chinese fonts.
BigTIFF is a special kind of TIFF, not compatible with the old kind of TIFF.
Apparently CS6 will open BigTIFF files BUT will not make them/save them. Files this size can only be saved as PSB.
Before CS5 there may have been plug-ins to buy - but I can't find them in Google - and this post mentions a product: Big TIFF/tiled TIFF in PS Creative Cloud but unless it writes PSB files that's not a way in to Photoshop.
Actually, BigTiff is an extension of the original tiff file format and is completely transparent to the original tiff. Once the writing size goes beyond 4 Gbytes, the old limit of tiff files, the output format switches automatically to BigTIff. For more information, go to BigTIff.org.
For any Adobe product, it is simply a manner of switching to the newer libtiff library and recompling.
Also, here is a translation of the original German post:
"Is there any way to open Photoshop CS 5 Big Tiff formats? Unfortunately, I have no chance to switch to CS 6. I'd be happy for help! Thank you very much"